Message-ID: <4ED8FF6D.7040108@usa.net>
Date: Fri, 02 Dec 2011 17:40:13 +0100
From: Alberto di Bene <dibene@usa.net>
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To: rsgb_lf_group@blacksheep.org
References: <E1RW9bG-0001fW-00.rn3aus-mail-ru@f214.mail.ru> <E1RWVQQ-00015Y-K7@post.thorcom.com>
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Subject: Re: LF: 16 bit vs 24 bit ADC?
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On 12/2/2011 4:53 PM, Bill de Carle wrote:
> My question is this: 
> In a practical situation with low QRN/QRM, would going to a 
> 24-bit ADC soundcard result in an ability to detect a weak LF signal 
> that would not show up on a Spectrum Lab display computed from 16-bit values?
In theory, of course yes. But you English-speaking people have a very pragmatical saying :
"The proof of the pudding is in the eating..."   :-)

It would be interesting to see weak signal receptions done both with a 16-bit sound card,
and 24-bit one, under the same conditions, and compare them.

But there is one thing that must be kept always in mind. Medium-to-high class 24-bit sound cards,
like e.g. the Delta 44, have a _nominal_ amplitude resolution of 24 bits.  Tests done by Leif
SM5BSZ (if I recall correctly) showed that only 19 to 20 of those 24 bits are meaningful....
the rest is just noise.

Perhaps, but this is just speculation on my side, going to a bit more professional 24-bit card,
like the Lynx2 or the E-MU 1212M, could gain another bit (maybe two) of resolution....
Both those cards use what is considered the best audio codec chip, the AK-5394A.

These are the specs of the E-MU card :  (I am not a reseller of them... :-)   )

http://dl.dropbox.com/u/15089947/emu1212mspec.gif

73  Alberto  I2PHD
 


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    On 12/2/2011 4:53 PM, Bill de Carle wrote:
    <blockquote cite=3D"mid:E1RWVQQ-00015Y-K7@post.thorcom.com"
      type=3D"cite">
      <pre wrap=3D"">My question is this:=20
In a practical situation with low QRN/QRM, would going to a=20
24-bit ADC soundcard result in an ability to detect a weak LF signal=20
that would not show up on a Spectrum Lab display computed from 16-bit val=
ues?</pre>
    </blockquote>
    <big><font size=3D"-1"><big><font face=3D"Tahoma">In theory, of cours=
e
            yes. </font></big></font></big>But you English-speaking
    people have a very pragmatical saying :<br>
    "The proof of the pudding is in the eating..." =A0=A0<span
      class=3D"moz-smiley-s1"><span> :-) </span></span><br>
    <br>
    It would be interesting to see weak signal receptions done both with
    a 16-bit sound card,<br>
    and 24-bit one, under the same conditions, and compare them.<br>
    <br>
    But there is one thing that must be kept always in mind.
    Medium-to-high class 24-bit sound cards,<br>
    like e.g. the Delta 44, have a <u>nominal</u> amplitude resolution
    of 24 bits.=A0 Tests done by Leif<br>
    SM5BSZ (if I recall correctly) showed that only 19 to 20 of those 24
    bits are meaningful....<br>
    the rest is just noise.<br>
    <br>
    Perhaps, but this is just speculation on my side, going to a bit
    more professional 24-bit card,<br>
    like the Lynx2 or the E-MU 1212M, could gain another bit (maybe two)
    of resolution....<br>
    Both those cards use what is considered the best audio codec chip,
    the AK-5394A.<br>
    <br>
    These are the specs of the E-MU card :=A0 (I am not a reseller of
    them...=A0<span class=3D"moz-smiley-s1"><span> :-) </span></span>=A0 =
)<br>
    <br>
    <img alt=3D"http://dl.dropbox.com/u/15089947/emu1212mspec.gif"
      src=3D"http://dl.dropbox.com/u/15089947/emu1212mspec.gif"
      moz-do-not-send=3D"true" height=3D"860" width=3D"698"><br>
    <br>
    73=A0 Alberto=A0 I2PHD<br>
    =A0 <br>
    <br>
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